Self-powered, portable devices typically rely on batteries to provide power. The batteries in these devices must be recharged or replaced periodically. Efforts to reduce the need for recharging and replacing batteries have included attempting to increase the power storage capacity of batteries and to lower the power consumption of the devices.
Some self-powered devices are integrated circuits and have all their components fabricated at the integrated circuit level. However, tying such devices to batteries or similar power sources is not suitable for some applications due the limitations of batteries.